17 Population Growth and Development

Atreyo Mondal and Gautam Kshatriya

Contents:

1. Introduction

2. Reasons for Population Growth

2.1. Geometric Progression

2.2. Arithmetic Progression

3. Population Dynamics

4. Total Population Growth Rate

5. Population Growth Forms

5.1. Exponential Growth Form (J – Shaped Growth Curve)

5.2. Sigmoid Growth Form (S – Shaped)

6. Population Structure (composition)

7. Population Pyramid

7.1. Pyramid with a Broad Base

7.2. A Bell – shaped Polygon

7.3. A Rectangular Polygon

7.4. An Urn – shaped Figure

8. What is the Demographic Transition

9. Why Do Fertility and the Pace of Population Growth Matter for Development

10. What is the Demographic Dividend and How is it a Window of Opportunity

11. Summary

Learning Objectives:

To know about the reasons for population growth
To know about different types of progression
To know about the different types of population growth forms
To know about the different types of population pyramid

1. Introduction

Anthropologists believe, that human species dates back at least 3 million years. For most of our history these distant ancestors lived a precarious existence as hunters and gatherers. This way of life kept their total numbers small, probably less than 10 million. However, as agriculture was introduced, communities evolved that could support more people.

World population expanded to about 300 million by A.D. (Ray Hall, 1993) and continued to grow at a moderate rate. But after the start of the Industrial Revolution in the 18th century, living standards rose and widespread famines and epidemics diminished in some regions. Population growth accelerated. The population climbed to about 760 million in 1750, reached 1 billion around 1800, and 6 billion by the end of the twentieth century (Fig. 1).

Fig. 1 World population accelerated after World War II

Source – United Nations Population Division, World Population Prospects, The 2008 Revision.

World population accelerated after World War II, when the population of less developed countries began to increase dramatically. After millions of years of extremely slow growth, the human population indeed grew explosively, doubling again and again; a billion people were added between 1960 and 1975; another billion were added between 1975 and 1987. Throughout the 20th century each additional billion has been obtained in a shorter period of time.

July 11, 1987 was designated as the day on which world population reached 5000 million- ‘a day to celebrate’, ‘a day to contemplate’. October 12, 1999 was also celebrated in which the population reached 6000 million.

It is estimated that population numbers had grown to 1000 million around 1800, and by 1900 the total was 1,700 million. By the end of the 1st half of the 20th century the figure was 2500 mill, and less than 40 years later had reached 5000 million, a huge figure in the context of the history of the world population growth. By 2000 the number has grown to 6,100 million.

The history of the world population growth can be divided into 2 periods. For most of the time that human beings have inhabited the planet, population has grown very slowly indeed. The pace of growth began to increase from around the beginning of the 18th century, accelerating to the very rapid rates characteristic of the 2nd half of the 20th century. During the 1960’s the rate of growth was 2 % per annum, a rate double that of the 1st half of the 20th century, which in turn was double that of the 19th century. (EPHTI, 2005)

Fig. 2 World Population Distribution by Region 1800-2050

Source: United Nations Population Division, Briefing Packet, 1998 Revision of World Population Prospects.

2. Reasons for Population Growth

Thomas Malthus, (1766-1834), English clergyman and economist in his “essay, “The Principles of Population”, hypothesized that there is relationship between economic development and population growth. He claimed that population was increasing faster than food production, and he feared eventual global starvation.

Malthus was criticized that he could not foresee how modern technology would increase food production, and that he considered people only as consumers, but they are also producers, since “with every mouth God sends a pair of hands”. However, his observations how populations increase and his arguments are important when there are fixed resources such as land, energy resources, etc. He suggested that populations tend to grow in geometric progression (Exponential), doubling in size every ‘n’ years depending on the population growth rate; while food supplies can at best grow in arithmetic progression.

2.1. Geometric Progression

A series of ordered numbers is said to be in geometric progression if the proportion of any two adjacent numbers is the same.

e.g. 3, 9, 27, 81 ……………..; or 1, 2, 4, 8, ……….. etc.

Population size over a period of years is said to follow a geometrical pattern of growth, if the change within a particular year is proportional to the population size at the beginning of that year.

2.2. Arithmetic progression

A series of figures is said to be in arithmetic progression, when the difference between any two adjacent figures is the same.

e.g. 3, 5, 7, 9, 11,…………………; or 1. 2, 3, 4, …….. etc.

Population size over a period of years is said to be in arithmetic progression, if the size changes by a constant amount each year.

The doubling time of a population is the number of years it would take for a population to double in size if the present rate of growth remained unchanged. Its purpose has been to emphasize how quickly populations can grow, doubling their numbers geometrically. Doubling time cannot be used to project future population size because it assumes a constant growth rate over decades, where as growth rates do change over time. To calculate doubling time, divide the number 70 (actually 69.3 for better accuracy) by the population growth rate expressed in percent. For example a country with a population growth rate of one percent would double its population in about 70 years; at 2% in 35 years; at 3% in 23 years.

Doubling Time = 70

Population Growth Rate

Malthus said that if the growth of population exceeds that of food, preventive checks such as continence (self resistance in refraining from sexual intercourse) and delayed marriage must be introduced; or Positive Checks, such as starvation or famine, disease and war will plague the society. He grouped these checks under the heading of “Misery and Vices”.

3. Population Dynamics

If we assume that the number of individuals entering a population (immigration), equals the number of leaving (emigration), population growth is the result of the increase of births over deaths. This relationship is summarized by a formula known as the balancing equation. It is expressed as:

P 2 = P1 + ( B – D) + ( I + E)

Where:-

P2 = Size of population for the year under consideration

P 1 = Size of population in the preceding year

B = Number of births between the two dates

D = Number of deaths between the two date.

I = Number of immigrants in the time under consideration (between P2 and P1) E = Number of emigrants in the time under consideration (between P2 and P1)

The differences between births and deaths in a population produces the Natural Increase (or Decrease) of a population. The rate of Natural Population increase is the rate at which a population is increasing (or decreasing) in a given year due to excess (or deficit) of births over deaths expressed as a percentage of the base population.

RNI = Births – Deaths X 100

Total Population

Birth Rate – Death Rats

Net Migration: is the difference between the numbers of persons entering a geographic area (Immigrants) and those leaving the area (emigrants).

4. Total Population Growth Rate

It is the rate at which a population is increasing (or decreasing) in a given year due to natural increase and net migration expressed as a percentage of the base population.

Total Growth Rate = Natural increase + Net Migration X 100

Total Population

5. Population Growth Forms

Populations have characteristic patterns of increase which are called Population Growth Forms. There are two patterns of population growth forms.

5.1. Exponential Growth Form (J – Shaped Growth Curve)

In this growth form density increases rapidly in exponential or compound interest fashion, when there is no environmental restrictions; and then stops abruptly as environmental resistance or other limits of resources become effective more or less suddenly. This resistance is the carrying capacity, the upper level beyond which no major increase can occur (K).

Graph

Fig. 3 Exponential Grow Curve (J – shaped)

5.2. Sigmoid Growth Form (S – Shaped)

In this growth form the population increases slowly at first (establishment or positive acceleration), then increases more rapidly (perhaps approaching a logarithmic phase), but soon it slows down gradually as the environmental resistance increases percentage wise (the negative acceleration phase), until a more or less equilibrium level is reached and maintained that is the carrying capacity, showing more or less an S – shaped curve.

Graph

Fig. 4 Sigmoid Growth Curve (S- shaped)

6. Population Structure (composition)

Aside from the total size, the most important demographic characteristic of a population is its population structure. Population structure refers to the composition of the population in terms of Age, sex, occupation, religion, educational status, geographical distribution, socio– economic status etc. The structure of a population is influenced or affected by births, deaths and migration and their predisposing factors.

The age – sex structure determines potential for future growth of specific age groups, as well as the total population. For these reasons the age structure has significant government policy implications. A population of young people needs a sufficient number of schools and later, enough jobs to accommodate them. Countries with a large proportion of older people must develop retirement systems and medical facilities to serve them. Therefore, as a population ages needs change from child care schools and jobs to jobs, housing, and medical care.

7. Population Pyramid

The age–sex structure of a country can be studied through population pyramids. Population pyramids show pictorially (graphically) the effects of the three factors that influence population. The overall shape of the pyramid indicates the potential for future growth. Population pyramids present the population of an area or country in terms of its composition by age and sex at a point in time. The series of horizontal bars in a pyramid represent the percentage contribution of each age and sex groups (often of five years age group interval) in the population. A glance at a population pyramid can tell a great deal about that population. One can easily see whether a population is young or old. By convention males are shown on the left and females on the right of the pyramid. Young peoples at the bottom and the elderly at the top. The ratio or percentage of the various age groups in a population determines the current reproductive status of the population and indicate what may be expected in the future.

The shape of the pyramid reflects the major influences on births and deaths, plus any change due to migration over three or four generations proceeding the date of the pyramid. The following four representations of population age – sex structure provide an overall example of what a pyramid for different levels of population growth would look like – rapid growth, slow growth, zero growth and negative growth.

Source – EPHTI,2005

7.1. A pyramid with a Broad Base

This indicates a high percentage of young population. Rapid population growth the low survivorship and high natality of human population in many developing countries result in a pyramidal stable age – structure, in which most of the population is young.

7.2. A Bell shaped Polygon

This indicates a moderate proportion of young to old Population. Slow population growth.

7.3. A Rectangular Polygon

In a more developed countries high survivorship and low natality produce populations with an almost rectangular, stable age structure in which all age groups are equally abundant. Zero population growth.

7.4. An Urn – shaped Figure

This type of shape indicates a low percentage of young Population, which is characteristic of a declining Population. Negative population growth.

Throughout human history, the world’s population had grown slowly and by the beginning of the 20th century was only 1.6 billion people. Today, after only 110 years, the world’s population has surpassed 7.1 billion people.

During this time, the world has witnessed tremendous development—including innovations in health care, education, infrastructure, and technology—but more than 2 billion people still live in poverty and remain left out of this progress. The great challenge leaders of the world face today is to reduce poverty and inequity, and improve people’s lives without compromising the environment and the well-being of future generations.

At the same time, world population continues to increase by more than 80 million people a year, with most of the growth occurring in the world’s least developed countries. By 2050, according to the United Nation’s medium projection, the world’s population will increase to 9.6 billion people and will continue to grow through 2100. (United Nations Population Division 2011.) This continued growth has strong implications for health, well-being, and economic development.

8. What is the Demographic Transition

Figure

Note: Natural increase or decrease is the difference between the number of births and deaths. The birth rate is the number of live births per 1,000 population in a given year. The death rate is the number of deaths per 1,000 population in a given year.

Source: Carl Haub and Toshiko Kaneda, 2011 World Population Data Sheet (Washington, DC: Population Reference Bureau, 2013); and (for burials in 1693 and 1694): E.A. Wrigley, Population and History (New York: McGraw Hill, 1969).

The theory of the demographic transition is that most countries were once characterized by high birth and death rates, and little population growth— During the transition period of Stage 1.

Stage 2—a decline in mortality often precedes and is faster than a decline in fertility, resulting in population growth because there are more births than deaths.

In Stage 3, birth rates decline until eventually in Stage 4 they reach the same level as death rates and population growth slows.

While many countries have followed this pattern of demographic change, the timing of the transition and pace of mortality and fertility declines has varied greatly among countries, resulting in the different rates of population growth seen across countries today. In Europe and North America, this transition took place over several centuries. Death rates and birth rates declined as health and living conditions improved, age at marriage increased, family planning services became available, desired family size decreased, and women obtained higher levels of education and more employment out of the home.

In many developing countries, the demographic transition began in the middle of the 20th century and changes have taken place over a period of just decades. Today, many developing countries particularly in Asia and Latin America have low mortality and fertility rates and population growth is slowing. At the same time, the world’s least developed countries are still in early or intermediate stages of the transition with birth and death rates declining, but high compared to the rest of the world. Experts debate whether these countries will follow the classic demographic transition model. Many of the least developed countries are experiencing slow or stalled fertility declines and will not transition to the next stage until fertility levels decline substantially.

Today demographers are also discussing a fifth stage that occurs if a country’s slow population growth turns into a period of population decline. In this fifth stage, population size eventually declines after birth rates fall below replacement level fertility, meaning the average woman has fewer than two children during her lifetime.

It is critical that leaders understand where their countries are in the demographic transition, how to make progress toward lower birth and death rates, and finally, how to plan effectively for slowed growth, population decline, and eventual stabilization. (Maura Graff, M., & Bremner, J., 2014)

9. Why Do Fertility and the Pace of Population Growth Matter for Development

One important dimension of population dynamics is fertility. Fertility levels declined during the last century in most developed countries, and those countries will experience little or no population growth in the years ahead. As shown in Figure 1, nearly all population growth today and in the coming decades will be in the developing countries where high fertility levels persist, especially in the least developed countries where the average woman continues to have four or more children during her lifetime (Washington, DC: Population Reference Bureau, 2013).

At the same time, unintended pregnancies contribute to high fertility and population growth, which shape the size and age structure of a nation’s population, and determine the demand for social services and natural resources as well as the size of the labor force. These factors affect the scale of development challenges and the strategies and investments required to manage them.

Most leaders understand that development strategies depend on sustained investments in health care, education, employment, and natural resources. However, rapid population growth in many developing countries threatens to undermine these investments and exacerbate the challenges of poverty, maternal and child health, HIV/AIDS, gender discrimination, and job creation. It also puts pressure on agricultural land, fresh water, and energy resources.

10. What is the Demographic Dividend and How is it a Window of Opportunity

The demographic dividend is the accelerated economic growth that may result from a rapid decline in a country’s fertility and the subsequent change in the population age structure (James N. Gribble and Jason Bremner, “Achieving a Demographic Dividend,” Population Bulletin 67, no. 2 (2012).

Early in the demographic transition, when a country has experienced high levels of fertility and rapid population growth, there are more people in the younger age group than the adult working-age group. A decline in fertility and fewer births each year means that over time, there will be a decline in the number of children in relation to the working-age adults. This period when there are more workers than young dependents is a window of opportunity for a country to facilitate accelerated economic growth. However, a demographic dividend is not automatic for those countries with large young populations today. Increased investments in family planning, education, and child survival are needed to advance fertility decline and create the conditions for a demographic dividend.

Investments in education, economic policies, and infrastructure, as well as good governance are also needed to convert the opportunity of fertility decline into accelerated economic growth. Key policies and investments are needed to strengthen health care and education systems to ensure a healthy and skilled workforce. At the same time, governments need to carry out reforms and infrastructure investments that attract higher levels of investments, create jobs, ensure a better-educated labor force, and accelerate economic growth.

Summary

World population expanded to about 300 million by A.D. and continued to grow at a moderate rate. But after the starting of the Industrial Revolution in the 18th century, living standards rose and widespread famines and epidemics diminished in some regions. Population growth accelerated. The population climbed to about 760 million in 1750, reached 1 billion around 1800, and 6 billion by the end of the twentieth century.

Over the last 200 years, countries around the world have followed similar patterns of change from high to low birth and death rates, leading demographers to develop a model called the demographic transition divided into stages which many countries have followed this pattern of demographic change, the timing of the transition and pace of mortality and fertility declines has varied greatly among countries, resulting in the different rates of population growth seen across countries today.

The age–sex structure of a country can be studied through population pyramids. Population pyramids show pictorially (graphically) the effects of the three factors that influence population. The shape of the pyramid reflects the major influences on births and deaths, plus any change due to migration over three or four generations proceeding the date of the pyramid.

There factors that affect the scale of development challenges and the strategies and investments required to manage them like in case of unintended pregnancies which contribute to high fertility and population growth, which shape the size and age structure of a nation’s population, and determine the demand for social services and natural resources as well as the size of the labor force.

In the case, when a country has experienced high levels of fertility and rapid population growth, there are more people in the younger age group than the adult working-age group. A decline in fertility and fewer births each year means that over time, there will be a decline in the number of children in relation to the working-age adults. This period when there are more workers than young dependents is a window of opportunity for a country to facilitate accelerated economic growth.

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References

EPHTI, (2005). Lecture Notes For Health Science Students on Population and Development Ethiopia Public Health Training Initiative, The Carter Centre, the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education.
Hall, R., (1993). Update, World Population Trends.
Haub, C., & Kaneda, T., (2013). World Population Data Sheet. (Washington, DC: Population Reference Bureau, 2013).
Gribble, N. J., & Bremner, J., (2012). “Achieving a Demographic Dividend,” Population Bulletin 67, no. 2 (2012).
Graff, M., & Bremner, J., (2014). A Practical Guide to Population and Development.
United Nations Population Division 2012, World Population Prospects: The 2012 Revision. New York: United Nations.

Suggested Readings

Survey of Research in Demography by P.B. Desai.
An Introduction to Population by O.W Kenneth and Kammeyer.
Dynamics of Population and Family Welfare in India by Srinivasan and Mukerjee.
Principals of Population Genetics by , A., Bhende and T. Kanitkar.